Parity violation in Th-232 neutron resonances above 250 eV - art. no. 025501

The analysis of parity nonconservation (PNC) measurements performed on Th-2 32 by the TRIPLE Collaboration has been extended to include the neutron ene rgy range of 250 to 1900 eV. Below 250 eV all ten statistically significant parity violations have the same sign. However, at higher energies PNC effe cts of both signs were observed in the transmission of longitudinally polar ized neutrons through a thick thorium target. Although the limited experime ntal energy resolution precluded analysis in terms of the longitudinal asym metry, parity violations were observed and the cross section differences fo r positive and negative neutron helicities were obtained. For comparison, a similar analysis was performed on the data below 250 eV, for which longitu dinal asymmetries were obtained previously. For energies below 250 eV, the p-wave neutron strength functions for the J = 1/2 and J = 3/2 states were e xtracted: S-1/2(1) = (1.68 +/-i 0.61) x 10(-4) and S-3/2(1) = (0.75 +/- 0.1 8) x 10(-4). The data provide constraints on the properties of local doorwa y states proposed to explain the PNC sign effect in thorium.